WO1994010390A1

WO1994010390A1 - Column base

Info

Publication number: WO1994010390A1
Application number: PCT/FI1993/000447
Authority: WO
Inventors: Kari Viljakainen
Original assignee: Tartuntamarkkinointi Oy
Priority date: 1992-11-04
Filing date: 1993-11-03
Publication date: 1994-05-11
Also published as: FI531U1; FIU920659U0

Abstract

Column base consisting of a downwards tapering lower part (11) sinkable into the ground and a barrel-shaped upper part (5) in which the column is mounted, said upper (5) and lower (11) parts being separate components. The upper and lower parts are provided with curved thrust elements. Moreover, the curved thrust elements of the upper and lower parts are provided with holes placed at mutually corresponding locations, the hole in the upper thrust element being larger than the hole in the lower thrust element, said upper and lower parts being joined together by their thrust elements by means of a barlike threaded part going through the holes, onwhich at least one tightening element (9) provided with an internal thread corresponding to the thread of the treaded part can be screwed, permitting the required adjustement of inclination in a vertical plane and of rotation relative to the vertical axis.

Description

COLUMN BASE

The present invention relates to a column base as defined in the introductory part of claim 1.

The columns along the sides of roads and streets e.g. for traffic signs, signals and illuminators are traditionally erected on concrete elements placed in the ground. First, a hole is dug in the ground at the site of erection and the concrete element is positioned in the hole by using a filler packed around the element. To enable the concrete element to transmit the required loads, the filler has to be compacted in thin layers, generally by previously moistening the filler material. This method of founding a column is laborious. First, the compact roadside banking structure is broken up and then compacted again. In addition to an excavator, a suitable filler, sand, crushed aggregate or gravel, and the water needed to moisten it have to be transported to the site of erection of the column.

To reduce the amount of work, various other types of column base have been tried, e.g. a steel tube base for traffic signs which is rammed into the earth. The tube is provided with a pointed end and vanes for transmitting the load. The traffic sign post is then mounted directly inside this base tube. An example of this type of column base solution is found in Finnish patent application 870213. When a base tube like this is being rammed into the ground, it may hit a stone or a piece of gravel which forces it into a tilted position, in which case it has to be extracted from the ground and rammed in again.

With the growth of the traffic volume and driving speeds, safer column structures have been developed to improve road safety. In a collision, a safe column can come off its base or be broken so as to slow down the speed of the colliding vehicle. In an ideal case, the column is bent down under the vehicle, stopping it safely. Flexible column structures have been developed especially for illuminator posts by providing the sheet metal tube structure with an attenuated zone which, in a collision situation, acts as a joint. A yielding column structure like this is more expensive than the conventional steel column, so its use has been restricted to busy roads and risky road stretches.

The object of the present invention is to eliminate the draw¬ backs of previously known column structures. The features characteristic of the column base of the invention are pre¬ sented in the claims attached. The two-part column base and the joint between the parts allow adjustment as required. When a vehicle hits the column, the joint between the parts will break and the column will come off its base or bend down under the vehicle. The base is easy to drive into the ground and to adjust into the correct position, and it permits the use of ordinary columns in yielding structures.

In the following, the invention is described in detail by the aid of an example by referring to the attached drawings, in which

Figure 1 presents the lower part of the column base of the invention, figure 2 the upper part, figure 3 the base in assembled form and figure 4 the base when broken at the joint.

The lower part of the column base shown in figure 1 is manu¬ factured from two bent sheet metal plates 11 tapering towards the lower end and welded together to form a crosswise vane structure. This is the part of the column base which is driven into the ground. Attached to the top of the lower part is a steel plate 1 bent upwards in the shape of a spherical surface and cut into a rectangular or circular form. In the middle of this plate is a hole 2. Fixed to the underside of the steel plate 1 is a hexagonal nut 3 with a vertical threaded bar 4 (oriented in the direction of the vertical axis of the base, indicated by a dotted broken line) attached to it. Parts 1 - 4 act as joining and adjusting elements of the lower part, to which the upper part of the column base is fastened.

The upper part of the column base shown in figure 2 consists of a barrel 5 having a circular or rectangular plate 6 at¬ tached to its bottom, said plate 6 being bent downwards into a spherical shape corresponding to the spherical surface of the lower part, the curvature and form of this plate 6 corre¬ sponding to those of the plate 2 of the lower part. The plate 6 is provided with a hole 7 in the middle, the diameter of said hole exceeding that of the threaded bar 4. Each side wall of the barrel part 5 of the column base is provided with one or two sharp triangular bent edges 8 protruding towards the inside of the barrel, said edges running throughout the length of the barrel. A column can be fixed in the barrel part 5 e.g. by using the same plastic collar rings as are used with concrete elements. A wooden column is held tight between the edges 8, which fasten it to the barrel by means of friction.

The upper and lower parts of the column base are joined together as shown in figure 3 by placing the upper part on top of the lower part so that the threaded part goes through the hole 7 in plate 6 of the upper part, and by fastening the parts together by means of a hex nut 9, with a washer 10 shaped like a spherical surface under it. The upper part of the column base can be rotated relative to the vertical axis (dotted broken line) of the base by loosening the nut 9 and turning the upper part. As the larger hole 7 in plate 6 provides a tolerance for adjustment, the angle of inclination of the upper part can also be adjusted by loosening the nut 9 and turning the upper part in relation to the vertical axis.

In this way, the base structure allows the required adjust¬ ment of inclination relative to the vertical direction and of rotation of the column relative to the vertical axis. More¬ over, the joining elements attach the upper part to the lower part with a joint transmitting the forces.

The form of the top part of the column base can be modified in that instead of a square sectional form of the barrel, a rectangular or a round cylindrical form is used, depending on the form of the column. Thus, the same carrier part (lower part) can be used with different top parts according to the material and the size and form of the cross-section of the column in question, yet the two parts are joined together using the technique described above.

For the collision load, the threaded bar 4, which together with the nut 3 fixed to its lower end forms a bolt structure, is so designed that it will'break when a vehicle hits the column (the screw is hardended to such a shear strength that it will break under a certain load) . At present, the yield strength is defined in Finland for a 900-kg vehicle which collides head-on against the column at a speed of 32 km/h. When the fixing bar is broken, the column will come off the lower part of the base and the vehicle will move on at an almost unchanged speed.

The speed of the vehicle can be slowed down in a collision situation by designing the juncture between the upper and lower parts of the column base so that it will form a joint structure that is tough in a breaking situation. One solution is to use a tensile, flexible screw whose fixing part (nut 3 or bolt head) will, in a breaking situation, bend the steel plate 1 of the lower part and ultimately break through it. Another method is to make the spehrically bent steel plate 1 of the lower part wider than the vane parts 11 (figure 4) . When a vehicle collides against the column, the protruding portion of the steel plate 1 (the portion extending outside the vanes) of the base will bend at the point indicated by the arrow while the bar 4 will yield, thus forming a flexible joint. It is obvious to a person skilled in the art that different embodiments of the invention are not restricted to the ex¬ amples described above, but that they may instead be varied within the scope of the following claims.

Claims

1. Column base consisting of a downwards tapering lower part (11) sinkable into the ground and a barrel-shaped upper part (5) in which the column is mounted, said upper (5) and lower (11) parts being separate components, characterized in

that the upper and lower parts are provided with curved thrust elements (1,6),

and that the curved thrust elements (1,6) of the upper and lower parts are provided with holes (2,7) placed at mutually corresponding locations, the hole in the upper thrust element being larger than the hole in> the lower thrust element, said upper and lower parts being joined together by their thrust elements by means of a barlike threaded part (4) going through the holes, on which at least one tightening element (3,9) provided with an internal thread corresponding to the thread of the threaded part (4) can be screwed, permitting adjustment of inclination in a vertical plane and of rotation relative to the vertical axis as required.

2. Column base according to claim 1, characterized in that, with respect to the collision load, the threaded part (4) is so designed that it will break in a collision situation.

3. Column base according to claim 1, characterized in that, in a collision situation, the juncture of the upper and lower parts of the column base constitutes a substantially tough, jointlike and breakable structure formed by using a substan¬ tially tough, flexible threaded part (4) whose tightening element (3) below the thrust element (1) of the lower part, in a breaking situation, bends the platelike thrust element (1) of the lower part and ultimately breaks through it.

4. Column base according to claim 1, characterized in that, in a collision situation, the juncture of the upper and lower parts of the column base constitutes a substantially tough, jointlike and breakable structure formed by making the thrust element (1 ) of the lower part wider than the rest of the lower part (11), so that, in a collision situation, the protruding edge of the thrust element (1 ) is bent down as the threaded part (4) yields.

5. Column base according to claim 1 , characterized in that the threaded part (4) is substantially oriented in the direc¬ tion of the vertical axis.